net/ice/base: allow flash read with arbitrary size

net/ice/base: allow flash read with arbitrary size

Refactor ice_read_flash_module so that it takes a size and a length
value, rather than always reading in 2-byte increments. The
ice_read_nvm_module and ice_read_orom_module wrapper functions will
still read a u16 with the byte-swapping enabled.

This will be used in a future change to implement reading of the CIVD
data from the Option ROM module.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
Acked-by: Qiming Yang <qiming.yang@intel.com>